1. Viruses Doesn’t belong to any kingdom -It’s not a plant or an animal.
-It’s not a fungi, protist, or bacteria.
WHAT IS A VIRUS?

2. A virus is an infectious agent made up of nucleic acid (DNA or RNA) wrapped in a protein coat called a capsid.
Viruses have no nucleus, no organelles, no cytoplasm or cell membrane—Non-cellular
This is why it does NOT belong to any kingdom. vs

3. Viruses with RNA that transcribe into DNA are called retroviruses.
Viruses have either DNA or RNA but NOT both.
Viruses with RNA that transcribe into DNA are called retroviruses.
Viruses are parasites—an organism that depends entirely upon another living organism (a host) for its existence in such a way that it harms that organism.
HIV Infected Cell
(This is the reason why HIV is so incurable.)
A flea is a parasite to a dog and is harmful to the dog.

4. Bacteriophage—viruses that infect bacteria
Capsid (protein coat)
inside contains either
RNA or DNA
2. Flu (influenza), HIV
DNA or RNA
Surface Marker
Capsid (protein coat)

5. Bacteriophage—a virus that infects bacteria (bacteria is the host)
Capsid
Nucleic Acid
Bacteriophage—a virus that infects bacteria (bacteria is the host)

6. C. Nonviral particle
Has protein only, no DNA or RNA (cause of mad cow disease and Creutfeldt-Jacob disease in humans)—Prions (affects the brain and is always fatal)
No DNA or RNA!

7. D. Replication is how a virus spreads.
A virus CANNOT reproduce by itself—it must invade a host cell and take over the cell activities, eventually causing destruction of the cell and killing it. (The virus enters a cell, makes copies of itself and causes the cell to burst releasing more viruses.)
DNA/RNA is copied.
DNA/RNA injected into cell.
Virus attaches to cell.
Step 3
Step 2
Step 1
Virus copies itself.
Cell bursts (lyses) and releases new viruses.
Step 4
Step 5

8. Certain viruses can only attack certain cell types
Certain viruses can only attack certain cell types. They are said to be specific.
Example: The rabies virus only attacks brain or nervous cells.
Surface Markers
Virus
Receptor Sites
It’s like the pieces of a puzzle. The ends have to match up so only certain pieces fit.
Cell

9. A virus recognizes cells it can infect by matching its surface marker with a receptor site on a cell.
Virus
Surface Markers
Cell
Receptor Sites

10. Importance: Beneficial: *Harmful Causes disease—pathogenic
Disease producing agent—pathogen
Human Diseases: Warts, common cold, Influenza (flu), Smallpox, Ebola, Herpes, AIDS, Chicken pox, Rabies
Viruses disrupt the body’s normal equilibrium/balance
Viruses can be prevented with vaccines, but NOT treated with antibiotics.
(antibiotics treat bacteria)
Beneficial:
Genetic Engineering—harmless virus carries good genes into cells.

12. Virus Living Cell RNA or DNA core (center), protein coat (capsid)
Cell membrane, cytoplasm, genetic material, organelles
Structure
Copies itself only inside host cell--REPLICATION
Asexual or Sexual
Reproduction
DNA and RNA
Genetic Material
DNA or RNA
Growth and Development NO
YES—Multicellular Organisms
Obtain and Use Energy NO
YES
Response to Environment
YES NO
Change over time NO
YES

13. Are viruses living? NO ONE
How many characteristics of life do viruses possess?
ONE
*Genetic Material
Are viruses living? NO

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